Background: The ability to modulate emotional responses, or emotion regulation, is a key mechanism in the development of mood disruptions. Detection of a neural marker for emotion regulation thus has the potential to inform early detection and intervention for mood problems. One such neural marker may be the late positive potential (LPP), which is a scalp-recorded event-related potential reflecting facilitated attention to emotional stimuli. In adults, the LPP is reduced following use of cognitive emotion regulation strategies such as reappraisal. No studies to date have examined the LPP in relation to cognitive emotion regulation in children, and whether the LPP is related to parent-report measures of emotion regulation and mood disruptions. Methods: To examine this question, high-density electroencephalograph (EEG) was recorded from 20 children (M age = 87.8 months, SD = 18.02; 10 girls) while they viewed unpleasant emotional pictures following either a directed negative or neutral interpretation of the picture. Results: As predicted, the LPP was smaller following neutral versus negative interpretations at posterior recording sites, except for younger girls (aged 5-6). The timing of this effect was later than that reported in studies with adults. For all children, greater modulation of the LPP by neutral interpretations was associated with reduced anxious-depressed symptoms, whereas larger LPPs for both interpretation types were associated with greater mood symptoms and worse parent-reported emotion regulation. Conclusions: Results suggest that the LPP may represent a clinically relevant neural marker for emotion regulation and mood disruptions.